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2006 A6 3.2 misfiring and losing power as it warms up

Been struggling with this for a little while now. Car runs like a clock for about five minutes on a nice cold day. Half that starting in warm weather. VCDS does see the odd misfire in cylinders 4 and 5, but you wouldn't notice if you weren't watching the program.
After that the right side exhaust becomes visible (it's not thick, but is white-ish and smells of gasoline), and the car begins to misfire more heavily in cylinders 4 and 5. Eventually, it swaps over to cylinder 6. The car begins shaking and losing power and these misfires progress.

Depending on the degree of misfiring, an appropriate amount of throttle resolves the misfiring almost 100% of the time, and the car instantly smooths out. Taking foot back off gas afterwords results in an even rougher idle.

The exhaust seems to come out of the affected side hot, and in more of a constant flow rather than the well-defined bursts coming from the other side. There is still some pressure/pattern, but it mostly just blows out in a steady stream.

Does anyone have any experience / suggestions?

Additionally, does anyone know where to buy replacement grommets for the valve cover bolts? I was told that I should be replacing all of the bolts every time I do the gasket because they come with new grommets, but I'm not overly keen on spending $10 CDN on each bolt just for the grommets. It's a small expensive relatively, so I will do so if necessary,
but does anyone know if it is simply a generic grommet that I can ask for at a local store? My local parts store wasn't sure when I showed them, and I want to be sure that the job is done correctly of course.

My current plan of action is replacement the valve cover and intake manifold gaskets because I've noticed a little bit of oil around the valve cover, and VCDS claims low manifold pressure while running rough, but it's within spec while smooth.

Really I'm just hoping that someone has run into a similar kind of situation and may have a bit of insight. All feedback is welcome and appreciated.

Brother it sounds like the catalytic converter is clogged up on that side. Behavior matches. At idle runs like crap because it's backing up on that side of the engine, but any additional amount of exhaust (applying throttle) builds up enough to blow through the clogged catalytic so it seems to run normal... until it drops to idle again. What's funny about this is that you MAY not even get a check engine light for it, from my experience. You technically SHOULD, but not always.

The easiest way to confirm this is to get under the car when engine is at operating temp and with an infrared thermometer gun (cost like $20-$25US):
- In a working catalytic system, the OUTLET of the cat should be hotter than the inlet side (as the cat is basically a big clay oven)
- in a clogged/ bad cat, the INLET will be hotter than the outlet (since the pressure is building up there)

Good luck and let us know what you find!

EDIT- as for the VC bolt grommets, I too read that somewhere but I didn't worry about it when I did my VC gaskets. All the grommets were in great shape so I had no need to replace them. I got maybe 37k since I did the VC gaskets and no leaks from the grommets here

Brother it sounds like the catalytic converter is clogged up on that side. Behavior matches. At idle runs like crap because it's backing up on that side of the engine, but any additional amount of exhaust (applying throttle) builds up enough to blow through the clogged catalytic so it seems to run normal... until it drops to idle again. What's funny about this is that you MAY not even get a check engine light for it, from my experience. You technically SHOULD, but not always.

The easiest way to confirm this is to get under the car when engine is at operating temp and with an infrared thermometer gun (cost like $20-$25US):
- In a working catalytic system, the OUTLET of the cat should be hotter than the inlet side (as the cat is basically a big clay oven)
- in a clogged/ bad cat, the INLET will be hotter than the outlet (since the pressure is building up there)

Good luck and let us know what you find!

EDIT- as for the VC bolt grommets, I too read that somewhere but I didn't worry about it when I did my VC gaskets. All the grommets were in great shape so I had no need to replace them. I got maybe 37k since I did the VC gaskets and no leaks from the grommets here

This was exactly the response I was looking for. Can't wait to get back down there and see where we can get.